For example, a medium processing device such as a banknote pay-in/pay-out device to perform various transactions related to a medium, such as a banknote, is widely employed (see, for example, Japanese Patent Application Laid-Open (JP-A) No. H02-012592, Japanese Patent Application Laid-Open (JP-A) No. 2012-48313, and Japanese Patent Application Laid-Open (JP-A) No. 2010-211340).
Generally, the medium processing device is configured such that a medium storage box for internally storing such a medium is attachable to and detachable from the main body of the medium processing device.